All the traditional lens components known to the present are provided with only two optical surfaces, i.e., the front surface and the rear surface. This construction limits the range within which the focal length can be varied. Although this problem has been ameliorated, to some extent, by the development of zooming lens groups or combination-lens products, either the resultant products are bulky, or only a limited extent of change in focal length can be obtained. Therefore, we are still dependent largely upon the use of interchangeable lens system for providing a wider variation range of focal length. For example, a camera user typically has to change to a wide-angle lens for wide-angle applications. Similarly, a telephoto lens is typically required for taking close-up shots of far-away objects. Recently, variable focal length cameras, from wide-angle to telephoto, have become available in the market. These cameras are very bulky and sometimes do not provide very good qualities.
With the ever-growing popularity of conventional and video cameras, and the need to have both the wide-angle and telephoto capabilities built into the same optical device without having to change optical lens components, it thus becomes very desirable to have an optical lens component, which can be used alone or in conjunction with other optical lens components, to provide a wide range of focal lengths, including both the wide-angle and the telephoto capabilities, with the same lens.